Give the ground state electron configuration for Se. A) [Ar]4s23d104p4 B) [Ar]4s24d104p4 C) [Ar]4s23d104p6 D) [Ar]4s23d10 E) [Ar]3d104p4
The Correct Answer and Explanation is:
Expand to view model thoughtschevron_righteditmore_vert
Correct Answer
A) [Ar]4s²3d¹⁰4p⁴
Explanation
To determine the ground state electron configuration for an element, we follow a set of rules, primarily the Aufbau principle, which dictates that electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels. The electron configuration describes the distribution of an atom’s electrons in these atomic orbitals.
- Identify the Element and Atomic Number: First, locate Selenium (Se) on the periodic table. Selenium is in Group 16 and Period 4. Its atomic number (Z) is 34. In a neutral atom, the number of electrons is equal to the atomic number, so a neutral Se atom has 34 electrons.
- Use the Noble Gas Abbreviation: To simplify the configuration, we can use the noble gas that precedes the element in the periodic table. For Selenium (in Period 4), the preceding noble gas is Argon (Ar), which is at the end of Period 3. Argon has an atomic number of 18, so its configuration ([Ar]) represents the first 18 electrons (1s²2s²2p⁶3s²3p⁶). This accounts for the core electrons.
- Place the Remaining Electrons: We need to place the remaining 34 – 18 = 16 electrons into orbitals according to the Aufbau principle. The filling order after the 3p subshell (the last filled subshell in Argon) is 4s, then 3d, then 4p.
- The 4s subshell is filled next. It can hold a maximum of 2 electrons, giving us 4s². We have now accounted for 18 + 2 = 20 electrons.
- Following the 4s subshell, the 3d subshell is filled. It can hold a maximum of 10 electrons, resulting in 3d¹⁰. We have now placed 20 + 10 = 30 electrons.
- Finally, the remaining 34 – 30 = 4 electrons are placed in the 4p subshell. This gives us 4p⁴.
- Combine the Parts: By combining the noble gas core with the configuration of the remaining electrons, we get the complete ground state electron configuration for Selenium:[Ar]4s²3d¹⁰4p⁴
